This invention relates to cleaning solutions. In one aspect, this invention relates to cleaning solutions for removing uncured polyurethane resin systems from surfaces of processing equipment or any other surface on which it is undesired, while in another aspect, this invention relates to cleaning solutions comprising one or more dibasic esters, water and a catalyst useful for promoting a reaction between water and an isocyanate. In yet another aspect, this invention relates to aqueous cleaning solutions comprising at least one dibasic ester, water, a catalyst and a cosolvent and/or surfactant capable of coupling with the dibasic ester and water. In still another aspect, this invention relates to using the cleaning solutions as a cleansing flush for polyurethane foam processing equipment.
Many, if not most, polyurethane resin systems are two-part systems comprising a liquid isocyanate and a liquid polyol. In the manufacture of materials from these systems, typically each component is metered and pumped separately to a mixing head in which they are blended and either simultaneously or subsequently discharged or "shot" onto a surface or injected into a mold. The mixed isocyanate and polyol react quickly with one another, even in the absence of a catalyst, and as such, the blend quickly begins to gel or solidify. Because these systems gel or solidify quickly, and because a residual amount often remains within the processing equipment after use, e.g. within the mixing head after discharge or injection, the equipment head often requires cleansing or flushing after each use.
Preferred cleaning solutions exhibit good cleaning efficiency, low health hazard, low flammability hazard, ease of reclamation and/or disposal, and environmental safety. Traditional cleaning solutions contain a large portion of methylene chloride, an effective cleansing agent with many desirable characteristics, but one that is coming under increasing government regulation for both health and environmental reasons. Of the commercially available alternatives, those cleaning solutions based on mixtures of dibasic esters, generally known as "DBE", are preferred because not only do they possess desirable human and environmental safety characteristics, but they also possess a relatively good cleaning efficiency and a low flammability hazard. However, these DBE-based cleaning solutions also exhibit an undesirable low-loading characteristic, i.e. they gel after a period of time during which the isocyanate-polyol reaction completes polymerization. As such, recycling or disposing of used cleaning solution is both difficult and expensive.